Is prescribing pot ‘the right thing to do’? Doctors debate the issue

It was a discussion with a patient, who attempted suicide after failing to respond to antidepressants, which recently prompted Dr. David Juurlink of Sunnybrook Health Sciences Centre to do something he had never done.

The man explained how after years of suffering anxiety and work-related stress, and not responding to psychotropic drugs, he only felt at peace when smoking a joint during his evening walk with the dog.

For the first time in his 20-year career, Juurlink, an internist and head of the Division of Clinical Pharmacology and Toxicology, suggested the patient talk to his family doctor about medical marijuana.

“This was a revelatory clinical encounter for me,” recalls Juurlink in a commentary published Monday in the Canadian Medical Association Journal. “Endorsing the use of medicinal cannabis for this patient was the right thing to do.”

He wasn’t the only one weighing in on the issue of whether doctors should prescribe marijuana. So too did Dr. Meldon Kahan, medical director of Substance Use Service at Women’s College Hospital, and Dr. Anita Srivastava, a family physician at St. Joseph’s Health Centre, who also co-authored a commentary. The two opinion pieces are part of a new debate format in the CMAJ that will feature experts with opposing views.

Kahan and Srivastava argue that when it comes to chronic pain — the most common reason for prescribing pot — there is “weak evidence” that it’s effective. And, they note, there are “short and long-term safety risks.”

“Smoking cannabis has been associated with an increased risk of motor vehicle crashes, schizophrenia, mood disorders and addiction,” they write, adding risk is higher among those under age 25.

The issue is timely given Health Canada’s introduction in April of new rules around medicinal marijuana, which have garnered criticism from groups such as the Canadian Medical Association and the College of Family Physicians of Canada. Government used to license medicinal marijuana users, but it’s now up to doctors and nurse practitioners to prescribe pot, which must be purchased from approved commercial producers.

Kahan and Srivastava say physicians “urgently need prescribing guidelines to help us understand the evidence, to counsel our patients and know when and how to prescribe cannabis.”

Guidelines, they note, should include indications, precautions, contraindications and recommended doses. They argue the only clear indications, or valid reason to use marijuana medicinally, is for neuropathic pain and spasticity from multiple sclerosis. (This means patients currently smoking pot for common pain conditions, such as fibromyalgia and lower back pain, would be excluded.) And, they suggest reasons for not prescribing pot would likely include a history of psychosis, substance abuse, mood disorders and anxiety.

Although Health Canada permits prescriptions of up to 5 grams of weed a day, they argue a maximum safe dose is 400 mg of cannabis that contains less than 9 per cent THC, the main psychoactive ingredient. Licensed producers, however, are selling strains with up to 25 per cent THC, so they suggest that any physician prescribing pot specify that the THC content not exceed 9 per cent.

Juurlink urges doctors not to reject marijuana as a medicine simply because it makes them uncomfortable. Nor should physicians “invoke concerns about effectiveness and safety without acknowledging that the other drugs we might prescribe carry similar and often much heavier baggage.”

When it comes to treating chronic pain, says Juurlink, “many analgesics we might prescribe instead of cannabis are themselves not supported by robust evidence.” And with regards to safety, “the direct toxic effects of cannabinoids are simply dwarfed by those of opioids and non-steroidal anti-inflammatory drugs.”

“Many patients are injured or die every year from the medications we prescribe for pain,” writes Juurlink. “A case can be made for the judicious prescribing of cannabis, particularly for patients who have previously experienced meaningful symptomatic improvement with its use, and for those who have not benefited from or are intolerant of conventional medications.”